A virtual machine (VM) is a portion of software that, when executed on appropriate hardware, creates an environment allowing the virtualization of an actual physical computer system (e.g., a server, a mainframe computer, etc.). The actual physical computer system is typically referred to as a “host machine,” and the operating system (OS) of the host machine is typically referred to as the “host operating system.” Typically, software on the host machine known as a “hypervisor” (or a “virtual machine monitor”) manages the execution of one or more virtual machines or “guests”, providing a variety of functions such as virtualizing and allocating resources, context switching among virtual machines, etc. The operating system (OS) of the virtual machine is typically referred to as the “guest operating system.”
A VM may comprise one or more “virtual devices,” each of which may map to a physical device of the host machine (e.g., a network interface device, an I/O device such as a CD-ROM drive, a disk array, etc.). A virtualization management system, or “virtualization manager,” can manage the allocation of resources from host machines to VMs, monitor the status of the VMs, as well as the progress of commands and processes being executed by the VMs, and generally manage operations in the system.